In a grommet (a fastener) formed by a grommet main body and a fixation pin, there is the following grommet. In the grommet, at an insertion time of the fixation pin into the grommet main body, in a case wherein a locking claw formed at an end of the fixation pin is not positioned directly above a fixing protrusion formed inside the grommet main body, there is formed a chamfer portion (a cam portion), slidingly contacting with the locking claw of the fixation pin, and urging a rotation of the fixation pin up to that position, at an entrance of the grommet main body (see Patent Document 1).
In such a grommet, whichever direction the fixation pin is inserted into the grommet main body, both members are smoothly engageable. However, when both members are separated, there is no alternative but to pull the fixation pin out of an inside of the grommet main body by a force with a strength of releasing such an engagement.